engine miss mystery

Hi Jack,

That's an interesting thought. I have flown this plane for the past 4 years, more than a 1000 hours of flight time. I would think if it was a problem like that it would have come up before now. Several years ago I added a second oil cooler to keep the oil temps down on 110+ degree days, but before that I had high (top of the yellow) oil and coolant temps but never had misses.

Hi Walt,

Good answer to all questions. Not quite ready to give up on water - I have never used an ethanol blend(E10) so the next bit is speculation:

I have heard that ethanol can separate from the base petrol and is hydroscopic.

Separation may change the RON (octane rating) - I think this may be an urban myth

Being hydroscope it attracts water - this is correct and may have a bearing on how you manage the fuel in storage, especially the fuel in the aircraft tank, which is open to atmosphere (water vapour).

You check the fuel from the bowser for water & ethanol % - do you check the fuel in the aircraft?

37 Gals (140L) E10 -

  Does it all go into the aircraft ?

  Do you fuel after flight or befor?

  What quantity might you store?

  For how long?

What sort of container(s) do you use and are they air/gas tight?

On Jacks pre ignition  problem - This sound like it may be related to fuel type. Do you use AVGas? If so, there may be a lead build up that is the root cause of the preignition.

Walt - You added an additional oil cooler - what were the oil temperature  (Climb Out & Cruise) before you did that and now after?

Do you have a fuel return line with pilot jet 35 restrictor?

I would suspect a fuel problem. I would drop the carb float bowls and just check for debris that could be sucked into the jets momentarily blocking it giving a misfire. I have experienced this in the past and found small black particles in the bowl. I cleaned it all out and the problem went away.